Expanded adhesive paper, cylindrical lithium ion battery cell and adhesive pasting method thereof

Abstract

The present application belongs to the technical field of winding battery cell, and particularly relates to an expansion adhesive paper, a cylindrical lithium ion battery cell and a method for pasting the expansion adhesive paper. The expansion adhesive paper comprises: a double-sided adhesive layer for sealing and ending the outer layer of the winding battery cell; an expansion layer arranged outside the double-sided adhesive layer; a hot melt adhesive layer arranged outside the expansion layer; and a through hole penetrating through the double-sided adhesive layer, the expansion layer and the hot melt adhesive layer. The present application improves the electrolyte infiltration of the conventional termination adhesive tape by arranging the porous on the expansion adhesive paper. The expansion adhesive paper provided by the present application can initially accommodate more electrolyte in the expansion layer, improves the liquid retention capacity of the battery cell, and can significantly improve the cycle life of the cylindrical lithium ion battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of winding battery cells, and particularly relates to an expanded adhesive paper, a cylindrical lithium ion battery cell and a method for pasting adhesive on the battery cell. BACKGROUND

[0002] With the continuous improvement of the level of science and technology, lithium batteries are gradually widely used in various industries. In the existing battery cell manufacturing technology, after the positive and negative electrode sheets and the isolation film are wound by a winding machine, a PET single-layer termination adhesive tape is pasted at the end position of the isolation film, so that the bare battery cell is shaped and the tab is welded into the shell. For example, patent CN107845819A discloses a full-automatic winding machine for lithium-manganese cylindrical batteries, which uses a termination adhesive tape supply mechanism to paste a termination adhesive tape on the wound battery cell. In this scheme, the termination adhesive tape cannot penetrate into too much electrolyte, and pasting on the surface of the bare battery cell will affect the wicking of the wound battery cell and store more electrolyte. Moreover, the adhesive tape cannot store electrolyte, and the electrolyte is insufficient during the later cycle, which accelerates the cycle performance decay of the battery. SUMMARY

[0003] In view of the above problems in the prior art, the purpose of the present application is to provide an expanded adhesive paper, a cylindrical lithium ion battery cell and a method for pasting adhesive on the battery cell. The present application improves the electrolyte wicking of the conventional termination adhesive tape by providing multiple pores on the expanded adhesive paper. The expanded adhesive paper provided by the present application can initially accommodate more electrolyte in the expanded layer, improve the liquid retention capacity of the battery cell, and significantly improve the cycle life of the cylindrical lithium ion battery.

[0004] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0005] The first aspect of the present application provides an expanded adhesive paper, which comprises:

[0006] A double-sided adhesive layer for sealing the outer layer of the wound battery cell;

[0007] An expanded layer provided outside the double-sided adhesive layer;

[0008] A hot melt adhesive layer provided outside the expanded layer;

[0009] A through hole penetrating through the double-sided adhesive layer, the expanded layer and the hot melt adhesive layer.

[0010] The present application improves the electrolyte wicking of the conventional termination adhesive tape by providing multiple pores on the expanded adhesive paper. The expanded adhesive paper provided by the present application can initially accommodate more electrolyte in the expanded layer, improve the liquid retention capacity of the battery cell, and significantly improve the cycle life of the cylindrical lithium ion battery.

[0011] As a preferred embodiment of the above inflation tape, the double-sided adhesive layer comprises a polyester film and an acrylic layer arranged on both sides of the polyester film.

[0012] As a preferred embodiment of the above inflation tape, the material of the inflation layer comprises polystyrene.

[0013] As a preferred embodiment of the above inflation tape, a fire-retardant layer is arranged between the double-sided adhesive layer and the inflation layer.

[0014] According to the present application, the fire-retardant layer can protect the internal part of the battery even if an accident occurs in the later stage.

[0015] As a preferred embodiment of the above inflation tape, the material of the fire-retardant layer comprises an acrylic adhesive and aluminum hydroxide.

[0016] Here, the acrylic adhesive has adhesion and can bond the inflation layer; the aluminum hydroxide has fire-retardant property.

[0017] As a preferred embodiment of the above inflation tape, the thickness of the double-sided adhesive layer is 5-20 um (for example, 5 um, 10 um, 15 um or 20 um), the thickness of the inflation layer is 35-50 um (for example, 35 um, 40 um, 45 um or 50 um, etc.), the thickness of the hot melt adhesive layer is 5-15 um (for example, 5 um, 10 um or 15 um, etc.), and the thickness of the fire-retardant layer is 6-10 um (for example, 6 um, 8 um or 10 um, etc.).

[0018] The second aspect of the present application provides a cylindrical lithium ion battery cell, which comprises a winding structure cell, the cell comprising a winding tail end; and the inflation tape according to the first aspect, the double-sided adhesive layer being arranged at the winding tail end for sealing the outer layer of the cell.

[0019] The third aspect of the present application provides a method for pasting the inflation tape on a cylindrical lithium ion battery cell, which comprises the following steps:

[0020] S1, using the inflation tape according to the first aspect to seal the winding structure cell;

[0021] S2, rolling the inflation tape to make the inflation tape adhere to the cell;

[0022] S3, putting the cell obtained in step S2 into a shell, welding a cover plate, and then injecting liquid after vacuum baking.

[0023] The cylindrical lithium ion battery manufactured by the gluing method provided by the application is extruded on the swelling layer during formation and capacity distribution or charge and discharge cycles, so that the hot melt adhesive layer is extruded from inside to outside, the pressure gradually increases and is more uniform compared with the hot melt adhesive extruded from outside to inside in the prior art, the bubbles in the hot melt adhesive can be significantly reduced, and the effective bonding area is increased.

[0024] In the gluing method, as a preferred embodiment, the cylindrical lithium ion battery is a full-tab cylindrical lithium ion battery.

[0025] In the gluing method, as a preferred embodiment, the length of the swelling adhesive paper is not greater than the length of the wound structure of the battery cell, and the width of the swelling adhesive paper is not greater than the circumference of the wound structure of the battery cell.

[0026] In the gluing method, as a preferred embodiment, the rolling is cold rolling.

[0027] Compared with the prior art, the application has at least one of the following beneficial effects:

[0028] 1. The application improves the electrolyte infiltration of the conventional termination adhesive by providing the swelling adhesive paper with a plurality of holes, the swelling adhesive paper provided by the application can initially contain more electrolyte stored in the swelling layer, improves the liquid retention capacity of the battery cell, and can significantly improve the cycle life of the cylindrical lithium ion battery.

[0029] 2. The application adopts the punching design, which not only improves the electrolyte infiltration of the conventional termination adhesive, but also better ensures the swelling of the swelling layer in the electrolyte, the swelling layer is effective after the battery cell is injected into the shell, the swelling layer extrudes the hot melt adhesive layer, and the adhesion effect of the shell and the bare battery cell is improved.

[0030] 3. The swelling layer can initially contain more electrolyte stored in the swelling layer due to three-dimensional swelling after swelling, improve the liquid retention capacity of the battery cell, reduce the initial electrolyte, and the by-products of the initial electrolyte affect the initial cycle attenuation; the swelling layer exerts pressure on the battery cell after being effective, which can improve the battery cell formation interface, and the pressure increases with the increase of the cycle, and the pressure cycle can improve the cycle life

[0031] 4. The swelling layer is effective, the pressure is larger, and the bare battery cell is better fixed, the problems of tab tearing and diaphragm folding caused by dropping and vibration are improved. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The structure schematic view of the swelling adhesive paper provided for the embodiment 1 of the application;

[0033] Figure 2 The structure schematic view of the double-sided adhesive layer in the swelling adhesive paper provided for the embodiment 1 of the application;

[0034] Figure 3 The structure diagram of the expanded adhesive paper provided for the embodiment 2 of the present application.

[0035] Wherein, 1, double-sided adhesive layer; 2, expansion layer; 3, hot melt adhesive layer; 4, through hole; 5, flame retardant layer; 11, polyester film; 12, acrylic layer. DETAILED DESCRIPTION

[0036] In order to further understand the present application, the preferred embodiments of the present application are described below in conjunction with the examples, and the protection scope of the present application includes but is not limited to the following examples. The following examples are only used to illustrate the advantages and effects of the technical scheme of the present application, and do not constitute a limitation on the protection scope of the present application. Equivalent replacements made by those skilled in the art based on the present application all belong to the protection scope of the present application.

[0037] Unless otherwise defined, the technical terms used in the following examples have the same meanings as generally understood by those skilled in the art to which the present application belongs. The experimental reagents used in the following examples are all conventional biochemical reagents unless otherwise specified; the amounts of the experimental reagents used are all conventional reagent amounts in experimental operations unless otherwise specified; and the experimental methods used are all conventional methods unless otherwise specified.

[0038] The first aspect of the embodiment of the present application provides an expanded adhesive paper, which comprises: a double-sided adhesive layer for sealing and finishing the outer layer of a wound battery cell, the double-sided adhesive layer comprising a polyester film and an acrylic layer arranged on both sides of the polyester film, the thickness of the double-sided adhesive layer being 5-20 um; an expansion layer arranged on the outer side of the double-sided adhesive layer, the material of the expansion layer comprising polystyrene, the thickness of the expansion layer being 35-50 um; a hot melt adhesive layer arranged on the outer side of the expansion layer, the thickness of the hot melt adhesive layer being 5-15 um; a flame retardant layer arranged between the double-sided adhesive layer and the expansion layer, the material of the flame retardant layer comprising an acrylic adhesive and aluminum hydroxide, the thickness of the flame retardant layer being 6-10 um; and a through hole penetrating through the double-sided adhesive layer, the expansion layer, the flame retardant layer and the hot melt adhesive layer.

[0039] Here, the double-sided adhesive layer is in contact with the battery cell of a cylindrical lithium ion battery, and the hot melt adhesive layer is in contact with the shell of the cylindrical lithium ion battery.

[0040] The hot melt adhesive layer and the shell are pasted to play a role in bonding and fixing the battery cell, the expansion layer absorbs electrolyte to expand, the thickness of the negative electrode increases in the formation stage, and the hot melt adhesive layer is pressed from the inside to the outside, normal shell entering ratios such as 98% can be achieved by this way to make the hot melt adhesive layer pasted to the shell. Compared with the conventional operation of pressing from the outside to the inside, the expansion is more uniform, and the operation is more convenient.

[0041] In the existing battery manufacturing technology, the bare battery cell (the winding structure of the battery cell without any protection) of the cylindrical lithium ion battery is directly placed in the shell. Since there is a certain gap between the bare battery cell and the shell, relative sliding occurs between them, which affects the battery cell infiltration and liquid retention. When the battery cell flows into the market, the electrolyte deficiency of the battery cell in the later use stage will cause the cycle jump, interface failure, and other problems. During the use process, the customer may drop, vibrate, and other forms of mechanical impact, which can easily cause the tab to tear, damage, and even burn, etc.

[0042] The expanded adhesive paper provided by the embodiment of the present application reduces the gap between the battery cell and the shell after foaming, fixes the winding core, and serves as a buffer pad, thereby reducing the impulse caused by the drop of the battery cell. The problems caused by the abuse such as the tearing of the tab, the short circuit caused by the inversion of the diaphragm, and the damage of the pole piece can be obviously improved.

[0043] Due to the punching design of the adhesive paper, the dry moisture of the battery cell can evaporate from the pores of the adhesive paper, thereby reducing the baking time. After the electrolyte is injected, the electrolyte flows and accelerates the infiltration time between the holes. Meanwhile, the expansion layer is immersed in the electrolyte and foams (the characteristics of synthetic resin rubber, and the swelling of polystyrene brings foaming). More electrolyte can be stored in the expansion layer (the larger the area, the more the pores, and the more the stored electrolyte). Meanwhile, the initial excess electrolyte stored in the adhesive paper expansion layer can improve the overflow phenomenon. During the high-temperature formation stage of the battery cell, due to the expansion of the expansion layer and the rebound of the anode pole piece, the winding core is in contact with the shell and is pressed. The adhesion of the hot melt adhesive layer is enhanced, and the air between the inner extrusion adhesive layers is extruded. Due to the punching and extrusion, the adhesive paper is flat and wrinkle-free. Due to the expansion of the expansion layer and the rebound of the anode pole piece, the contact pressure between the winding core and the shell is larger after the formation. The large pressure formation can timely remove the gas generated during the formation and obtain a better formation interface.

[0044] The second aspect of the present application provides a cylindrical lithium ion battery cell, which comprises a winding structure of the battery cell, the battery cell comprising a winding tail end; and the expansion adhesive paper as described in the first aspect, the double-sided adhesive layer being arranged on the winding tail end for sealing and finishing the outer layer of the battery cell.

[0045] The third aspect of the present application provides a method for pasting the expansion adhesive paper on the full-tab cylindrical lithium ion battery cell, which comprises the following steps:

[0046] S1, using the expansion adhesive paper of the first aspect to seal and finish the winding structure of the battery cell;

[0047] S2, cold roller pressing the expansion adhesive paper to make the expansion adhesive paper adhere to the battery cell, the length of the expansion adhesive paper being not greater than the length of the winding structure of the battery cell, and the width of the expansion adhesive paper being not greater than the circumference of the winding structure of the battery cell;

[0048] S3, the battery cell obtained in step S2 is put into a shell, the cover plate is welded, and vacuum baking is performed before liquid injection.

[0049] In order to further understand the present application, the inflatable adhesive paper, cylindrical lithium ion battery cell and the adhesive method thereof provided by the present application are described in detail below in combination with examples, and the protection scope of the present application is not limited by the following examples.

[0050] Example 1

[0051] The present example provides an inflatable adhesive paper, which has the functions of tightly wrapping and fixing the wound cell, and also has the function of firmly fixing the cell and the shell (the outer part of the wound cell needs to be provided with a shell, and the cell and the shell can be adhered together by the adhesive paper to fix them, so that the cell will not slide relative to the shell), Figure 1 The structural diagram of the inflatable adhesive paper provided by the present example is shown in the figure, Figure 2 The structural diagram of the double-sided adhesive layer in the inflatable adhesive paper provided by the present example is shown in the figure, Figure 1 and Figure 2 As shown in the figures, the inflatable adhesive paper comprises: a double-sided adhesive layer 1, which is in contact with the wound cell and is used to seal the outer diaphragm of the wound cell, including a polyester film 11 and an acrylic layer (acrylic adhesive layer) 12 arranged on both sides of the polyester film 11; an inflatable layer 2 arranged on the outer side of the double-sided adhesive layer 1, the material of the inflatable layer 2 is polystyrene, and the inflatable layer 2 starts to expand after foaming when immersed in electrolyte; a hot melt adhesive layer 3 arranged on the outer side of the inflatable layer 2, which can bond the shell to firmly fix the cell and the shell; a through hole 4 penetrating through the double-sided adhesive layer 1, the inflatable layer 2 and the hot melt adhesive layer 3.

[0052] In the present example, the thickness of the double-sided adhesive layer 1 is 15um, the thickness of the inflatable layer 2 is 40um, and the thickness of the hot melt adhesive layer 3 is 8um.

[0053] In the present example, the double-sided adhesive layer 1 is mainly used to seal the outer diaphragm of the wound cell to ensure the stability of the wound cell structure, and to bond the inflatable layer, and the preparation method of the double-sided adhesive layer 1 is to take the polyester film as the base material, and coat the acrylic (acrylic adhesive) on both sides of the base material to obtain the double-sided adhesive layer 1; the hot melt adhesive (HMA) layer 3 is a layer of adhesive with hot melt property, which exhibits certain fluidity and adhesive function after being heated. For those skilled in the art, when sealing the wound cell, the tail end of the wound cell will be pasted with adhesive paper along the axial direction of the cell (the cell is a wound structure, and the axial line of the cell can be understood as the winding reference line when the cell is wound). The adhesive paper has a wide edge a and a long edge b, and the long edge b of the adhesive paper is parallel to the axial line of the cell, and the wide edge a of the adhesive paper is perpendicular to the axial line of the cell.

[0054] The embodiment provides a method for pasting glue on a full-tab cylindrical lithium ion battery cell, and the method comprises the following steps:

[0055] S1, the cell of the winding structure is sealed and finished by using the expanded adhesive paper provided in the embodiment, the distance a1 between the top end of the long side of the expanded adhesive paper and the top end of the pole piece (excluding the tab) in the axial direction of the cell is 1mm, the distance a2 between the bottom end of the long side of the expanded adhesive paper and the bottom end of the pole piece (excluding the tab) in the axial direction of the cell is 1mm, and the length of the wide side of the expanded adhesive paper is 1cm;

[0056] S2, the expanded adhesive paper is cold-rolled to be attached to the cell;

[0057] S3, the cell obtained in step S2 is put into a shell, a cover plate is welded, and electrolyte is injected after vacuum baking.

[0058] Embodiment 2

[0059] Figure 3 The structure diagram of the expanded adhesive paper provided in the embodiment is shown in the figure, Figure 3 the expanded adhesive paper provided in the embodiment is basically the same as that in embodiment 1, and the difference lies in that a fire-retardant layer 5 is arranged between the double-sided adhesive layer 1 and the expanded layer 2, the material of the fire-retardant layer 5 is acrylic adhesive and aluminum hydroxide, and the thickness of the fire-retardant layer 5 is 6μm.

[0060] The method for pasting glue provided in the embodiment is the same as that in embodiment 1.

[0061] Embodiment 3

[0062] The expanded adhesive paper provided in the embodiment is basically the same as that in embodiment 1, and the difference lies in that the thickness of the double-sided adhesive layer 1 is 10um, the thickness of the expanded layer 2 is 45μm, and the thickness of the hot melt adhesive layer 3 is 6um.

[0063] Comparative Example 1

[0064] The adhesive paper provided in the comparative example is a polyester film single-sided adhesive layer, which is a traditional winding cell sealing green glue, the lower structure of the polyester film single-sided adhesive layer is an acrylic adhesive layer, and the upper structure is a polyester film. Referring to the method for pasting glue provided in embodiment 1, the cell of the winding structure is sealed and finished by using the adhesive paper provided in the comparative example.

[0065] Comparative Example 2

[0066] The adhesive paper provided in the comparative example is basically the same as that in embodiment 1, and the difference lies in that the through hole 4 is not included.

[0067] Referring to the method for pasting glue provided in embodiment 1, the cell of the winding structure is sealed and finished by using the adhesive paper provided in the comparative example.

[0068] Performance test example

[0069] (1) Thickness change and electrolyte storage capacity test: at room temperature, the adhesive tapes provided by the examples and the comparative examples were respectively soaked in electrolyte (containing ethylene carbonate, diethyl carbonate and dimethyl carbonate with a mass ratio of 1:1:1, lithium hexafluorophosphate 1 mol / L) for 12 h, and the change rate in the thickness direction (change rate in the thickness direction = (thickness of the adhesive tape after soaking - thickness of the initial adhesive tape) / thickness of the initial adhesive tape) and the change in weight were tested, and the results are shown in Table 1.

[0070] (2) Cycle performance test method: the cylindrical lithium ion batteries prepared by the adhesive tape method provided by the examples and the comparative examples were subjected to cycle performance test, the test current was 1C, and the capacity retention rate at the Nth cycle = discharge gram capacity at the Nth cycle / discharge gram capacity at the first cycle.

[0071] Table 1

[0072]

[0073] As can be seen from Examples 1-3 and Comparative Examples 1-2, the expanded adhesive tapes provided by Examples 1-3 can initially accommodate more electrolyte to be stored in the expansion layer, improve the liquid retention capacity of the battery cell, and can significantly improve the cycle life of the cylindrical lithium ion battery. The applicant speculates that the reason may be that the expansion layer generates three-dimensional expansion after expansion, has higher porosity, can initially accommodate more electrolyte to be stored in the expansion layer, improves the liquid retention capacity of the battery cell, and reduces the free electrolyte in the battery cell, reduces the initial side reaction, and improves the initial capacity decay of the battery cell. With the increase of the number of battery charge and discharge cycles, the anode (negative electrode) thickness increases (lithium ions are inserted and de-inserted, the graphite layer spacing becomes larger after multiple times, which is macroscopically manifested as the thickness of the electrode sheet increases), which increases the thickness of the battery cell, the electrolyte in the expansion layer is squeezed and gradually released to be supplemented into the battery cell, and is preferentially supplemented to the point of electrolyte broken bridge, which can significantly improve the cycle life of the battery.

[0074] As can be seen from Examples 1-3 and Comparative Examples 1-2, the punching design can improve the expansion speed of the expanded adhesive tape, can initially accommodate more electrolyte to be stored in the expansion layer, and can more obviously improve the cycle life of the cylindrical lithium ion battery, and after the battery cell is pasted with the adhesive tape, the surface of the adhesive tape is flat without wrinkles, which can significantly reduce the proportion of poor appearance of the adhesive tape.

[0075] Obviously, the above embodiments are merely example for clearly illustrating but not limitation to the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments need not and can not be enumerated. The obvious changes or variations derived from the above description are still within the protection scope of the present application.

Claims

1. A method for taping a cylindrical lithium-ion battery cell, characterized by, The method comprises the following steps: S1, using the expansion tape to seal the winding structure of the battery cell; S2, rolling the expansion tape to make the expansion tape adhere to the battery cell; S3, putting the battery cell obtained in step S2 into the shell, welding the cover plate, and then injecting liquid after vacuum baking; The rolling is cold rolling; The expansion tape comprises: A double-sided adhesive layer for sealing the outer layer of the winding battery cell; An expansion layer arranged outside the double-sided adhesive layer; A hot melt adhesive layer arranged outside the expansion layer; A through hole penetrating through the double-sided adhesive layer, the expansion layer and the hot melt adhesive layer; The thickness of the expansion layer is 35-50μm.

2. The taping method of claim 1, wherein The length of the expansion tape is not greater than the length of the winding structure of the battery cell, and the width of the expansion tape is not greater than the circumference of the winding structure of the battery cell.

3. The taping method of claim 1, wherein The double-sided adhesive layer comprises a polyester film and an acrylic layer arranged on both sides of the polyester film.

4. The method of claim 1, wherein The material of the expansion layer comprises polystyrene.

5. The method of claim 1, wherein A fire-retardant layer is arranged between the double-sided adhesive layer and the expansion layer.

6. The method of claim 5, wherein The material of the fire-retardant layer comprises acrylic adhesive and aluminum hydroxide; And / or, the thickness of the fire-retardant layer is 6-10μm.

7. The method of claim 1, wherein The thickness of the double-sided adhesive layer is 5-20um; And / or, the thickness of the hot melt adhesive layer is 5-15um.

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